Eating when not hungry

I don’t understand why we should eat what we planned even if we are not hungry for it. I understand not swapping things out, like eat the apple you planned and not the strawberries that look good at the moment instead. But if I plan a snack and I’m not hungry then I’m not honoring myself at all. Why force it down and disregard my body like that? The next day I could not plan it but maybe I’m hungry for a snack that day. People’s hunger is not exactly the same every day … some days I’m more hungry than other days. I know I can choose this for myself, and I will, but I feel like I’m missing some kind of point so I’m curious to understand it better. I’m open to changing my point of view on this!